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            <h2 class="post-title">Python之上三角矩阵</h2>
            <div class="post-date">2019-09-15</div>
            
            <div class="post-content">
              <h1 id="numpytrium-k0">numpy.triu(m, k=0)</h1>
<blockquote>
<p>Upper triangle of an array.</p>
<p>Return a copy of a matrix with the elements below the k-th diagonal zeroed.</p>
</blockquote>
<p>例子:</p>
<pre><code>np.triu(np.ones(5), 0)
array([[1., 1., 1., 1., 1.],
       [0., 1., 1., 1., 1.],
       [0., 0., 1., 1., 1.],
       [0., 0., 0., 1., 1.],
       [0., 0., 0., 0., 1.]])
&gt;&gt;&gt; np.triu(np.ones(5), 1)
array([[0., 1., 1., 1., 1.],
       [0., 0., 1., 1., 1.],
       [0., 0., 0., 1., 1.],
       [0., 0., 0., 0., 1.],
       [0., 0., 0., 0., 0.]])
&gt;&gt;&gt; np.triu(np.ones(5), 2)
array([[0., 0., 1., 1., 1.],
       [0., 0., 0., 1., 1.],
       [0., 0., 0., 0., 1.],
       [0., 0., 0., 0., 0.],
       [0., 0., 0., 0., 0.]])
&gt;&gt;&gt; np.triu(np.ones(5), 3)
array([[0., 0., 0., 1., 1.],
       [0., 0., 0., 0., 1.],
       [0., 0., 0., 0., 0.],
       [0., 0., 0., 0., 0.],
       [0., 0., 0., 0., 0.]])
&gt;&gt;&gt; np.triu(np.ones(5)) - np.triu(np.ones(5), 3)
array([[1., 1., 1., 0., 0.],
       [0., 1., 1., 1., 0.],
       [0., 0., 1., 1., 1.],
       [0., 0., 0., 1., 1.],
       [0., 0., 0., 0., 1.]])
&gt;&gt;&gt; mask = np.triu(np.ones(5)) - np.triu(np.ones(5), 3)
&gt;&gt;&gt; mask
array([[1., 1., 1., 0., 0.],
       [0., 1., 1., 1., 0.],
       [0., 0., 1., 1., 1.],
       [0., 0., 0., 1., 1.],
       [0., 0., 0., 0., 1.]])
&gt;&gt;&gt; mask[3, 0:1] = 1
&gt;&gt;&gt; mask[4, 0:2] = 1
&gt;&gt;&gt; mask
array([[1., 1., 1., 0., 0.],
       [0., 1., 1., 1., 0.],
       [0., 0., 1., 1., 1.],
       [1., 0., 0., 1., 1.],
       [1., 1., 0., 0., 1.]])
</code></pre>

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